Trading Post will cease to publish a printed edition, meaning nearly 280 workers will be made redundant, including 95 print workers.
The Trading Post, owned by Sensis will now be published online only.
AMWU National Print Secretary Lorraine Cassin said workers in the printing industry need support.
“This is a terrible blow for Trading Post workers across Australia, particularly as many of them have been based in outer suburban areas where alternative work will be difficult to find,” said Ms Cassin.
The AMWU is working with Sensis and Trading Post workers to ensure they are assisted and receive their full entitlements.
The Trading Post is considered by many as an iconic Australian publication. Since its establishment, it has been the source for buying and selling among millions of Australians for work tools, cars, home furniture and toys.
It firmly established itself into Australian culture with its inclusion in the film The Castle, made by the Working Dog team in 1997.
The lead character of the film, Dale Kerrigan, makes the oft repeated line “Tell ‘em they’re dreaming” each time his son tells him the price of something quoted in the Trading Post.
Ms Cassin said the gag resonated with people because the newspaper has been such a big part of the way we live.
“The printing industry is adapting to change, but it is sad to see an icon like the Trading Post go this way.”
The AMWU said the announcement meant there was even more riding on an upcoming Federal Government decision on copyright laws affecting the printing of books in Australia.
“This announcement is another example of the pressure the printing industry is under and another reason for the Federal Government to reject proposals to limit the 30-Day rule which gives local book printers the first option on overseas titles.
“The Australian printing industry is a viable, profitable, and environmentally responsible industry that employs hundreds of workers directly, and thousands more in paper production, distribution and other related jobs.
“But removing the copyright restrictions that currently exist would see a reduction of $70 to 80 million per annum in revenue and cost jobs without any guarantee that prices will fall for consumers.
“Craig Emerson’s new proposal to keep the restrictions but force Australian publishers to make new releases available at the same time as they are released overseas would have the same result.
“We urge the Federal government to listen to the majority view that the removal of our existing copyright restrictions will drastically undermine and devastate Australia’s printing industry.”